What an AMAZING opportunity and race! It's definitely on my bucket list!
For a multi-stage ultra race like this one, you'll definitely need a comprehensive gear and nutrition plan. You'll also have to consider the added challenge of sand, and how to keep sand out of your shoes, and manage the special kind of chafing that comes from sand running.
With that, I feel you might benefit from a Virtual Outfitting appointment. Though you might have to make a late/early appointment due to your time zone, you'll still have the same conversation that you would have with one of our expert guides in-store. There, you can build your gear and nutrition list with one of our Green Vests.
Until you're able to schedule that conversation, check out this guide from TrainingPeaks on ultramarathon training. I also recommend Hal Koerner's Field Guide to Ultrarunning as well. And if you haven't already, start experimenting with nutrition on your training runs. Try lots of products to see what works best for you and your stomach, whether gels, liquid, chews, or solid food.
Enjoy the training! After the race, come back and post a race report with your amazing photos! (And make sure you have some sort of sandproof bag to keep your phone or camera in when you're running; I have some unfortunate experience with trying to dismantle a phone to remove sand, and it's not fun!)